Point detonating fuze



Oct. 1, 1957 H. B. LINDSAY POINT DETONATING FUZE Filed June 10, 1954INVENTOR firm/fy 5. L/NDSAY ATTORNEYS POINT DETONATDIG EFUZE Harvey B.Lindsay, Oakland, Caiif.

Application June 10, 1954, Serial No. 435,678

14 Claims. (Cl. 1132-73) Point detonating fuzes have been widely usedfor projectiles directed against personnel, light building construction,aircraft, and other targets, where it is desired to have the detonationoccur substantially simultaneously with impact. However, the presentlyavailable fuz es of this character possess a number of shortcomings inoperation,

construction, and/ or safety, which the fuze of this invention willeffectively overcome.

It is therefore an object of the present invention to provide a pointdetonating fuze which will function with far greater impact sensitivitythan the fuzes heretofore available, whereby the impact of the fuze onextremely light targets, such as tents or other very light constructionwill effect detonation of the associated projectile.

Another object of my invention is to provide a fuze of the typedescribed which will remain in safe unarmed position until theprojectile has been fired from the gun, notwithstanding blows, falls orother accidental loads imparted thereto during handling, transportationand firing.

A further object of the invention is to provide a fuze of the abovecharacter in which accidental pro-explosion of the detonator will notcause ignition or detonation of the main projectile charge.

A still further object of my invention is to provide a point detonatingfuze which possesses superior functioning reliability, and in whichmeans are provided to insure proper arming of the fuze in flight withoutthe dependence upon other forces than high centrifugal force alone,found in prior art devices.

Another object of this invention is to provide a fuze of the typedescribed which possesses relatively few working parts, and which may beproduced more economically than fuzes previously utilized.

The invention possesses other objects and features of advantage, some ofwhich, with the foregoing, will be set forth in the followingdescription of the preferred form of the invention which is illustratedin the drawing ac companying and forming part of the specification. Itis to be understood, however, that variations in the showing made by thesaid drawing and description maybe adopted within the scope of theinvention as set forth in the claims.

Referring to said drawing:

Figure 1 is a longitudinal cross-sectional view of the fuze of thepresent invention shown in its unarmed position, the general plane ofthe view being indicated by line 1--1 of Figure 2.

Figure 2 is a cross-sectional view taken substantially in the planeindicated by line 22 of Figure 1.

Figure 3 is a view similar to Figure 1, but showing the fuze in itsarmed position.

Z,8fi,ii Patented Oct. 1, 1957 Figure 4 is a portional cross-sectionalview taken substantially in the plane indicated by line 4-4 of Figure 2.

Figure 5 is a PQI iQnal cross-sectional view taken substantially in theplane indicated by line 55 of Figure 2.

Figure 6 is a perspective view of one of the pellet detonator stopmembers.

Figure 7 is a portional view of the rear end portion of a modified typeof firing pin and associated pellet stop members.

The fu e of the present invention is adapted for mounting on the frontend portion 12 of a projectile, the latter carrying the main detonatingor bursting charge which is arranged to be exploded when the fuzeand itsdetonator is actuated. It will be understood, however, that in someinstances, it may be desirable to utilize an auxiliary booster which isdetonated or ignited by the detonator and which in turn detonates theburster charge in the projectile. However, whether or not an auxiliarybooster is used has no bearing on the present invention.

As shown in the drawing, the fuze includes a relatively massivesubstantially cylindrical body 13 having threads 14 for attachment tothe projectile portion 12 and threads 16 for receiving the threaded endof the conically formed nose or ogive 17. The latter defines with thebody a chamber 18 in which the major portions of the fuze are disposed.The body is provided with an axially extending passage 19 which acts asa flash duct between the det- Ionator and burster as will be hereinafterexplained.

Secured to the front surface of the body 13 by means of screws 21 or thelike, is a yoke member 22, the latter having .flat peripheral portions23 in contiguous relation.- ship with peripheral portions of the body,and a forwardly .oifset central portion 24 of generally semi-cylindricalform. By referring to Figure 1, it will be seen that the body has acorresponding semircylindrical cavity 26 which defines with yoke portion24 a cylindrical chamber 27 for revolvably receiving a rotor 28. Thesize of the parts per.- inits relatively free rotation of the rotorwithin opening 27 about an axis perpendicular to and intersecting thelongitudinal axis of the projectile, ogive and flash duct.

Rotor 28 is provided with a diametrical bore 29 medially of its ends,and such bore, upon rotation of the rotor .(clockwise as shown in thedrawing) may move from the unarmed position shown in Figure 1 wherein itis axially aligned with a bore 31 in the fuze body to an armed positionwherein it is aligned with the previously mentioned flash duct 19. Thus,if a detonator is posiltioned in bore 29, and the bore is not alignedwith flash duct 19., setting off of the detonator will have no effect onthe projectile charge, and the force of the detonator explosion will bedirected along bore 29. However, as an added feature of safety, Iprovide a passage 32 from the bore 29 to the ogive chamber so that theexpanding gases from such van explosion may be spent in the relativelylarge chamber and escape therefrom through a passage 33 positioned atthe front end'of the nose on the longitudinal axis thereof. It should bementioned at this time that passage 33 is primarily for receptionof thefiring pin, to be explained in detail later, and its gas escape utilityis only a secondary feature.

;A detonator is arranged to be positioned within bore 29 and as hereshown, such detonator comprises a generally cylindrical pellet 36 whichmay consist of any of the-conventional fuze explosives such as azide,tetryl or the like. Referring to Figures ,1 and 3, the pellet will beseen to occupy a position in bore 29 radially ,outwardly from the centerof rotation and is maintained in such position by front and rear pelletstop members designated 37 and 38 respectively. The pellet stop membersare preferably constructed of extremely thin spring metal and haveparallel side portions 39, and end portions 41 lying on segments of acircle slightly larger which the point 55 protrudes.

than the diameter of bore 29. These end portions are adapted to engage apair of spaced peripheral grooves 42 and 43 in bore 29 and preferablyare on a larger diameter than the groove diameter so that'when seated inthe groove, the members will flex into the curvate shape indicated. Toinstall the pellet and its associated stop members, member 37 is firstintroduced into bore 29, forced past groove 43 and snapped into positionin groove 42, groove 42 being spaced from the rearend of firing pinportion 52, in unarmed position. The pellet 36 is then carefully pushedthrough the bore to stop 37, and stop 38 is then snapped into groove 43,the position of the latter spacing the rear end of the pellet from stopmember 38. It will be understood that'loading of the stopmembers andpellet is preferably performed after the rotor is positioned in theyoke, and it is for this reason that rotor bore 29 is aligned with theyoke bore 31 when the rotor. is in an unarmed position. Bore 31constitutes a loading channel .through which the pellet and stops areintroduced, and access may be made by unscrewing the ogive from the fuzebody and removing a threaded plug 46 from the end of bore 31, the use ofwhichplug 46 is optional.

. Where the detonator is formed of an explosive merely requiring animpact from the firing pin to effect detonation, the front stop membermay be made, of a solid piece of material. However, many modern fuzesemploy lead azide which is of substantially solid form, and which isactuated by piercing with a sharp instrument, such piercing causinglocal friction heating in the crystals 'which results in initiation of aflash and shock wave.

Accordingly, for such a detonator, the arrangement shown in Figure 7 ispreferably utilized. As there indicated,

the enlarged .firing pin head 54, later to be described 'in detail, isprovided with an axially extending point 55 which is adapted to passthrough a central aperture 47 formed in the front stop member 37.Although the point 55 will be axially spaced from stop 37, it might bepossible that in armed position, air pressure on the front end of thefiring pin would cause the latter to move rearwardly until the point 55penetrated the azide detonator. To prevent such an occurrence, I providean auxiliary stop member 40 engaged in a peripheralbore groove 45, suchstop having .a central aperture through However, stop 40 serves toprevent movement of the firing pin rearwardly until an actual impact iseffected on the firing pin nose, at

which time, stop 40 may be forced rearwardly to permit point 55 toforcibly penetrate the pellet through aperture 47 in stop member 37.

In conventional point detonating fuzes, the firing pin has consisted ofa straight piece of metal held in inoperative position by suitabledetents, preventing its being driven against the detonator. Certainoperational difiiculties accompany such an arrangement, and as animportant feature of this invention, the firing pin is not in firingposition until the fuze is armed. This is accomplished by utilizing ajointed firing pin consisting of a relatively long front portion 51 anda shorter rear portion 52, the latter preferably being bifurcated toreceive the rear end of portion 51 and is pivotally secured thereto by apin 53 or the like. Portion 52 is provided with a radially enlarged rearhead 54, which may include a sharp point 55 where an azide detonator isutilized, and such portion is slidably mounted in bore 29, with thepivot connection 53 being positioned exteriorly of such here. When thefuze is unarmed, as viewed in Figure l, the front portion of the firingpin is disposed entirely within the ogive chamber 18 and forms an angleof slightly more than ninety degrees with the rear portion 52, with theleading end 56 of the pin being positioned adjacent the nose opening 33.The rearend 57 of the pin is seated in a socket 58 formed in the fuzebody 13, and thus irrespective of any impact on the fuze, the firing pincannot actuate the pellet. V I

However, if the rotor is permitted to rotate into itsarmed position(shown in Figure 3), the rear firing pin portion 52 will likewise berotated, and due to the jointed connection at 53, the front firing pinportion 51 will be caused to move forwardly and upwardly until it isaxially aligned with the rear portion and capable of unitary axial Inthis armed position, the leading end 56 of the firing pin, extendsforwardly of the ogive movement therewith.

vided on yoke portion 24 which permits the aforesaid movement of thefiring pin relative thereto. Also, to provide clearance for the pivotalaction of the rear end 57 of the front pin portion, the rotor is notchedat 62 adjacent the front end of bore 29. Thus, clearance is obtained inboth the rotor and yoke to permit movement .of the firing pin from itsinoperative angularly disposed position to its operative axial position;

If bore 29 was of constant diameter, and the firing pin portion 52freely mounted therein for axial movement, it

might be possible for the pin to move forwardly from the firing positionshown in Figure 3 due to the creep effect. .Creep may be defined as thecontinuous inertia force resulting from the deceleration of theprojectile caused by air resistance, which tends to move fuze parts notdirectly exposed to air resistance towards the nose of the projectile.Although the force is not a great one, and in the armed position tendsto be nullified by the air pressure on the exposed-end of the firingpin, I prefer to positively maintain the firing pin in fixed relationtothedetonator. This may be accomplished by reducing the diameter of.bore 29 just forwardly of the rear pin head 54 as shown at 64, so thatpin portion 52'may freely move rearwardly, 1

such as when the front end 56 strikes a target, but will be restrainedfrom forward movement by the engagement of head 54 on the shouldersdefined at the juncture of bores 29'and 64.

Movement'of the rotor from its unarmed position to its armed position iseffected by the centrifugal force created by the rotation of the shellin flight, such rotation being imparted by the rifiing in the gunbore.Centrifugal force will tend to rotate the rotor within chamber 27,

and to assist such rotation, I provide a pair of cylindrical .lugs 67extending through the rotor which are not on the axial center line ofthe fuze. The ends of, the lugs extend beyond the rotary periphery,arcuate notches 68 being provided in yoke portion'24 and similar notches69 being provided in body 13 to permit movement of the lugs and therotor. Thus, these off-center weights will be more greatly affected bycentrifugal force and forcibly'rotate the rotor to the armed positionwhere further rotation is stopped by the lugs engaging a cut out portion71 on the fuze body 13.

Means are provided for retaining. the rotor in an unarmed position untilthe centrifugal force exerted on the lugs reaches a predetermined value.Preferably, this value is reached when the projectile is rotating atapproximately revolutions per second. As here shown, detents 72 areprovided adjacent each end of the rotor, each detent comprising a pieceof spring wire or'the like engaged in suitable V-shapecl notches 73 inthe end walls of yoke portion 24. One end of the Wire may be anchored ina cavity 74 in the rotor end walls with the distal portion of the detentresting in the housing groove. Thus, by regulating the spring size, thedetent can be freed from its seated position in the notch upon apredetermined centrif- .ugal force which may be readily calculated. Whencentrifugal force has reached this amount, thedetent will be It will beclear that in the armed posiasosnoo forced from the notch, and the rotorpermitted to rotate as hereinabove described. Clearance may be had forthe raised detent by providing a grooved portion 76 in the yoke housingalong the path of rotation of the detent with its rotor. If desired, asecond notch 77 may be utilized to receive the detent when the rotor hasmoved to its armed position.

From the above described detent arrangement it will be readilyunderstood that only extremely rapid rotation of the projectile (andfuze) will permit arming of the fuze. Thus, no accidental rolling of theshell will be sufiicient to impart the centrifugal force required topermit rotor rotation. As further safety factors, attention'is againdirected to the out of line or jointed firing pin, the reception of therear end of pin portion 51 held in socket 58, and the solid enclosure ofrotor bore in which the pellet is positioned. Even if an accidental blowwas given to the nose sufficient to crumple the ogive and distort thefiring pin in such a manner that portion 52 would be forced towards thepellet 36, pin portion 51 would engage the outer periphery of the rotor,halting movement of head 54 before pellet contact. However, even if thepellet was detonated from any cause, the provision of safety passage 32would prevent the explosive flash or force from reaching the mainprojectile charge.

With the foregoing description in mind, the phases of operation of thefuze will be discussed. We will as- .sume the fuze is mounted on aprojectile which is to be fired from a gun having a foot rifled barrel,one com- ,plete 360 degree twist of the lands in the barrel, and .amuzzle velocity of 2500 feet per second. Maximum acceleration of theprojectile will not occur until the projectile has left the mouth of thebarrel -or until the rapid outrush of highly compressed gases in thebarrel .have escaped. Upon full forward acceleration; the projectile andits associated fuse will be rotating at about 250 revolutions persecond, but even at this rate of rotation, the centrifugal force exertedon the rotor lugs will not be sufiicient to rotate the rotor, due to thebind- .ing of the setback force of the rotor in its housing created bythe pressure of the firing impact. Thus, notwithstanding immediaterotation of the projectile, the rotor will bind itself to its housinguntil forward acceleration of the projectile terminates, this usuallyoccurring from six to twenty inches beyond the mouth of the barrel.

After the initial period of acceleration, the main forces acting uponthe shell and fuze parts will be centrifugal force due to rotation,creep as previously described, and air pressure on the front end of thenose and firing pin. The latter two forces for the most part are minorand tend to neutralize each other. Therefore, as acceleration, setbackand binding forces have been eliminated, centrifugal force on therelatively massive rotor lugs 67 cause the rotor to rotate and overcomethe spring action of detents 72. This rotation effects a forwardmovement of firing pin portion 51, removing the same from socket 53, andurging the forward end 56 through the nose opening 33. At the same timethe two portions of the firing pin are brought into axial alignment withbore 29 and flash duct 19. When the rotor has been rotated to this armedposition, detents 72 will engage the notches 77 and serve to hold therotor in an armed position The foregoing will be accomplished inapproximately one-tenth of a second from the beginning of the projectileflight.

With the fuze armed, actuation requires only a slight contact on theexposed end 56 of the firing pin, the required impact being merelysufficient to have the head 54 strike the pellet stop 37 out of itsshallow groove 42 and with it to strike and detonate the pellet againstthe momentary resistance of pellet stop 38. As previously explained,where an azide detonator is used, the sharpened rear end 55 of thefiring pin would pass through 6 stop aperture 47 after displacing theauxiliary stop merriber 40 to pierce and detonate the pellet.

To prevent dust or other foreign matter from entering the ogive chamber,and to effectively seal the latter against accidental insertion ofobjects which could damage the firing pin, I provide a seal preferablyconsisting of a soft metal disk 80, such as lead, which may bereleasably retained in a peripheral groove 81 formed in the ogivepassage 33. This disk is constructed so that it maybe readily displacedfrom its sealing position upon arming of the fuze and forward movementof the firing pin.

From the foregoing description, the construction and operation of myfuze should be understood. It will be appreciated that the fuze of thisinvention is safer, more positive in action, and more economical toproduce than point detonating fuzes heretofore available. It Will befurther understood that the fuze is dynamically balanced in flight,thereby assuring higher accuracy. A final consideration includes thefact that most prior art devices could for reasons of safety only use avery small detonator, thereby requiring increasingly progressiveboosters and the like. By means of the novel safety vent arrangement,and other safety factors of this invention a more powerful detonatingcharge may be safely utilized so that its explosive flash or force mayreadily detonate the main projectile charge.

I claim:

1. A fuze comprising a longitudinally extending and substantially hollowbody provided with a base portion having a rotor chamber therein and alongitudinally extending passage adapted to communicate with saidchamher, a rotor rotatable in said chamber for rotation about an axisperpendicular to the longitudinal axis of said body, means defining adiametrical bore extending through said rotor perpendicular to the axisof rotation thereof and arranged to have one end thereof register withsaid passage in one position of rotation of said rotor, means in saidbore for receiving a detonator charge, and a firing pin having a firstportion extending into said bore from the other end thereof and a secondportion pivotally connected to said first portion exteriorly of saidbore.

2. A point detonating fuze comprising a longitudinally extending noseportion having an opening at the forward end thereof, a base at the rearend of said nose portion, means defining with the forward portion ofsaid base a substantially cylindrical rotor chamber having an axisnormal to the longitudinal axis of said nose portion, means defining alongitudinal passage in said base adapted to communicate with saidchamber, a generally cylindrical rotor slidably mounted in said chamberfor rotation therein about said chamber axis, said rotor having adiametrical bore positionable along a longitudinal axis in alignmentwith said passage in a first position of rotor rotation, means forselectively and releasably holding said rotor in said first and in asecond position of rotation, said rotor in said second position closingsaid passage, and a firing pin having a first element slidably mountedin said bore and a second element pivotally connected thereto exteriorlyof said bore, said elements being angularly related with a distal end ofsecond element adjacent said nose opening when said rotor is in saidsecond position and said elements being axially aligned with said distalend of said second element extending forwa rdly and exteriorly of saidnose portion through said opening when said rotor is in said firstposition of rotation.

3. A fuze of the character described comprising a conical nose portionhaving an axial opening at the apex thereof and defining a fuze chamber,means within said chamber defining a rotor housing, a rotor mounted forrotation in said housing about an axis substantially normal to the noseaxis, means defining a diametrical bore through said rotor lying in acommon plane with said nose axis, detent means normally maintaining therotor in a first position wherein said bore is angularly related to saidnose axis, axially offset weights on said rotor a 7 whereby centrifugalforce can effect rotation of said rotor to overcome said detent meansand rotate said rotor to a second position wherein said bore is axiallyaligned with said nose axis, a jointed firing pin having a first elementslidable in said bore and a second element pivotally connected theretoexteriorly of said bore, said second element having a distal portionmovable through said nose opening upon movement of said rotor from saidfirst position to said second position. I 4. A device as set forth inclaim 3 including means for stopping rotation of said rotor when thelatter has rotated from said first position to said second position. 5.A point detonating fuze assembly arranged to be attached to the frontend of a projectile carrying an explosive charge comprising alongitudinally extending tapered nose portion having an axial opening atthe front end thereof, a base positioned adjacent the rear end of saidnose portion and defining therewith a chamber, a substantiallycylindrical rotor positioned in said chamber with its axis perpendicularto and intersecting the longitudinal axis of said nose portion, meansfor rotatably supporting said rotor for rotation about said axis, adiametrical bore in said rotor having an axis lying in a planecontaining said nose portion axis, means for supporting a detonator insaid bore, a firing pin consisting of a first element slidable in saidbore and a second element pivotally attached thereto exteriorly of'saidrotor bore and having a front end adjacent said nose opening, means fornormally and releasably positioning said rotor with the bore thereofangularly related to the nose axis and with the elements of the firingpin disposed in regular relationship to each other and to saidlongitudinal axis, said means being releasable upon the rotation of saidfuze assembly and development of centrifugal force of predeterminedmagnitude to permit rotation of said rotor and to overcome saidpositioning means to a second position wherein said bore is aligned withsaid nose axis and the elements of the firing pin are axially alignedwith the front end of said second element extending axially through saidnose passage and the rear end of said first element adjacent saiddetonator supporting means, and an axial flash duct in said base wherebycommunication may be had between said bore and the explosive charge insaid projectile when said rotor is in said second position, and wherebysuch communication between said bore and said passage is wholly blockedby a solid portion of said rotor in said first position.

6. A device as set forth in claim 5 including a socket portion in saidbase for receiving the rear end of said second element when said rotoris in said normal position.

7. A fuze including a longitudinally extending nose portion defining achamber having axially aligned front and rear openings therethrough, asubstantially cylindrical rotor in said nose portion, meanssubstantially enclosing said rotor for supporting the latter forrotation about an axis perpendicular to and intersecting thelongitudinal axis of said nose portion, means defining a diametricalbore through said rotor having an axis lying in a plane containing saidnose axis, means defining a bore of substantially the same size as saidrotor bore in said supporting means having an axis lying in said planeand angularly related to said nose axis, duct means establishingcommunication between said latter bore and said chamber, said duct meanshaving an effective crosssectional area for the entire length thereof ofsubstantially the same size as said rotor bore, the total space occupiedby said bores and duct means being substantially less than the volume ofsaid chamber, a detent operatively connecting said supporting means andsaid rotor for normally positioning the latter with the rotor bore incommunication with the supporting means bore, a weight extending fromsaid rotor angularly related to said nose axis and adapted to overcomethe force of'the detent and permit rotation of said rotor upon thedevelopment of a predetermined centrifugal force created v V i, 8 l byrotation of said fuze, said rotor being movable to "a second positionwherein the rotor bore is axially aligned with said nose portionopenings, and a firing pin having a front end slidable through saidfront nose opening to extend axially forwardly thereof and a rearendslidable in said rotor bore for engaging a detonator in said bore uponimpact on the front end of the firing pin.

8. Apparatus as set forth in claim 7 in which said bore includes meansfor supporting a detonator therein, said means including a pair ofparallel detonator stop members spaced axially within said bore, andperipheral grooves in said bore for releasably receiving said stopmembers. p

9. A fuze as set forth in claim 7 including a pair of detonator supportmembers positioned in axially spaced relation in said rotor bore, one ofsaid members con- 'sisting of thin spring-like material having a centralaperture therein through which the rear end of said firing pin mayenter, and groove means for supporting said mem' bers in position insaid bore.

10. A- point detonating fuze comprising a longitudinally extending noseportion having axially aligned front and rear openings therethrough, asubstantially cylindrical rotor in said nose portion, meanssubstantially enclosing said rotor for supporting the latter forrotation about an axis perpendicular to and intersecting thelongitudinal axis of said nose portion, means defining a diametricalbore through said rotor having an axis lying in a plane containing saidnose axis, means defining a bore in said supporting means having an axislying in said plane and angularly related to said nose axis, meansdefining a passage leading from said latter bore exteriorly of saidrotor to within the nose portion, means normally positioning said rotorin a first position wherein the rotor bore is aligned and incommunication with the supporting means bore, means effecting rotationof said rotor to a second position upon application of centrifugal forceto said nose portion wherein the rotor bore is axially aligned with saidnose portion openings, means for supporting a detonator in said rotorbore, and a firing pin having a front end slidable through said frontnose opening and a rear end slidable in'said rotor bore for engaging adetonator in said bore upon. impact on the front end of the firing pin.

11. A fuze of the character described comprising a longitudinallyextending and substantially enclosed nose portion having front and rearopenings therein on the longitudinal axis thereof, a substantiallycylindrical rotor in said nose portion, means supporting said rotor forrotation about an axis normal to and intersecting said nose axis, saidrotor having a diametrical bore therethrough having an axis lying in aplane containing said nose axis, means normally maintaining said rotorin a first position wherein said bore is angularly related to said noseaxis, means permitting movement of said rotor to a second positionwherein said bore is aligned with said nose axis, a firing pin havingfirst and second elements, said first element being mounted for axialsliding movement in said rotor bore with the front end thereof extendingoutwardly of said bore, means pivotally connecting said front end tosaid second element adjacent the rear end of the latter about an axisparallel to the rotational axis of said rotor, the front end of saidsecond element being slidable in said front nose opening, said elementsbeing angularly related when said rotor is in its first position withthe front end of said second element disposed within said nose portion,and said elements upon movement of said rotor to said second positionbeing axially aligned with said front end extending through said frontnose opening.

12. A fuze as set forth in claim 1 further characterized by each of saidfiring pin portions lying in a plane containing said body axis and eachbeing angularly related to each other and to said axis in all positionsof rotor rotation except when said diametrical bore registers with saidpassage.

13. A fuze as defined in claim 1 in which the end of said body remotefrom said base portion is provided with References Cited in the file ofthis patent UNITED STATES PATENTS Watson Sept. 23, 1919 FOREIGN PATENTSGreat Britain May 25, 1926 France Nov. 12, 1938 Switzerland Dec. 1, 1941

